﻿/*
 * Copyright 2012 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 *
 * Copyright (c) The DotNetty Project (Microsoft). All rights reserved.
 *
 *   https://github.com/azure/dotnetty
 *
 * Licensed under the MIT license. See LICENSE file in the project root for full license information.
 *
 * Copyright (c) 2020 The Dotnetty-Span-Fork Project (cuteant@outlook.com) All rights reserved.
 *
 *   https://github.com/cuteant/dotnetty-span-fork
 *
 * Licensed under the MIT license. See LICENSE file in the project root for full license information.
 */

namespace DotNetty.Common.Utilities
{
    using System;
    using System.Collections;
    using System.Collections.Generic;

    struct CharSequenceEnumerator : IEnumerator<char>
    {
        ICharSequence charSequence;
        int index;
        char currentElement;

        internal CharSequenceEnumerator(ICharSequence charSequence)
        {
            if (charSequence is null) { ThrowHelper.ThrowArgumentNullException(ExceptionArgument.charSequence); }

            this.charSequence = charSequence;
            this.index = -1;
            this.currentElement = (char)0;
        }

        public bool MoveNext()
        {
            if (this.index < this.charSequence.Count - 1)
            {
                this.index++;
                this.currentElement = this.charSequence[this.index];
                return true;
            }

            this.index = this.charSequence.Count;
            return false;
        }

        object IEnumerator.Current
        {
            get
            {
                if (this.index == -1)
                {
                    ThrowHelper.ThrowInvalidOperationException_EnumeratorNotInit();
                }
                if (this.index >= this.charSequence.Count)
                {
                    ThrowHelper.ThrowInvalidOperationException_EnumeratorAlreadyCompleted();
                }
                return this.currentElement;
            }
        }

        public char Current
        {
            get
            {
                if (this.index == -1)
                {
                    ThrowHelper.ThrowInvalidOperationException_EnumeratorNotInit();
                }
                if (this.index >= this.charSequence.Count)
                {
                    ThrowHelper.ThrowInvalidOperationException_EnumeratorAlreadyCompleted();
                }
                return this.currentElement;
            }
        }

        public void Reset()
        {
            this.index = -1;
            this.currentElement = (char)0;
        }

        public void Dispose()
        {
            if (this.charSequence is object)
            {
                this.index = this.charSequence.Count;
            }
            this.charSequence = null;
        }
    }
}
